Much like throwing a baseball, there needs to be more muscle involvement from the rest of your body so as to not isolate the arm and shoulder.

The common injury from Toms/Thumbs is letting your arm reach full extention and having it pull your shoulder out of socket momentarily. This is hard to keep under control if you are using toms/thums to go over objects that are really tall.

Allow yourself to use a throwing motion similar to a baseball player throwing a ball in from the outfield to home plate. Start your run up with the disc close to your chest with your elbow bent. Make your body turn and reach the disc back (think throwing a ball) keeping the elbow bent and turning your upper building tension at the waist (Coiling up). Now plant that front foot and let your body uncoil starting at the waist letting your elbow lead the arm through the throw. (Just like pitcher). It is important to let your body follow through with the pitching motion just like a ball player does. This will prevent a sudden stop of the body and the arm continuing onto hyper extention.

Allright....but I need a little time. I have a tourney on saturday and then I'm on the bag for my daughter. We are getting ready for her tourney coming up in a couple weeks, I'll shoot it during one of her practice rounds.

I've dislocated my right shoulder a handful of times over the years, once or twice from throwing thumbers when I first started playing disc golf. I haven't had this happen in the past year or two due to a change in my form. I go through a similar motion as most when I throw the thumber, but when I get to the point of acceleration all of my power comes from my wrist and triceps. Thats it. I put absolutely no effort in with my shoulder muscles. I look at my shoulders role in the throw as simply guiding the disc while all power comes from the snap in my wrist and follow through with my triceps. My max distance for this is probably 220 tops but that's all I need when I use it. So give a whirl, hopefully it helps you out.

One more tip, I don't extend my arm/shoulder all the way back either. My elbow is bent the whole time and then straightens when I move the disc past my head moving forward. I start the thumber with my hand almost parallel to my head. That way I don't go too far back or up with my swing which can cause injury. It minimizes the torque on my shoulder that way too.

Stretching and warming up is key to prevent injury, I carry a baseball mit and softball with me and I throw for about 15 minutes before I play, Ill also do quite a few reps of holding the disc and practice my throwing motion with out releasing the disc, increasing my arm speed each rep.

Allow someone younger to throw your disc;>} My worn out shoulder/hand, wrist/body lets me know that I no longer can throw that to accomplish results.I now marvel/envy those who are able to throw these..ahh youth.

You're giving up way too much by not throwing them, IMO... I understand if some players have pre-existing injuries, but even they should be able to have an overhand approach throw in their arsenal. It takes barely any shoulder strength or torque to pop out a 150 to 200 foot thumber or tommy in situations where another shot type just won't cut it. Additionally, that overhand approach is quite a bit more accurate with just a little patience and practice.